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I now have over 4000 miles on my ISM re-power in my 96A3 bus. I'm now looking to increase efficiencies where I can. When I did the re-power I reused the muffler my 6v92 was using. The muffler is a Donaldson M120131 F1. This muffler has both the inlet and the outlet on the same end of the muffler and has fairly good flow ratings.

Exhaust Flow CFM @3" Hg 2" Hg 1" Hg----- ----- -----2913 2378 1682

The issue with this is the number of bends I had to put in my exhaust to connect to the muffler. The turbo outlet on the ISM points to the rear of the engine (front of the bus). So, I had to do an immediate 180 turn to reorient the exhaust towards the back. Then I had to do another 180 turn to go down and into the muffler inlet (now exhaust is flowing to the front of the bus in the muffler). Then the muffler redirects the exhaust back another 180 degrees and forces the exhaust to exit out the rear of the muffler. So, you can see there are a lot of turns in the exhaust system. I'd like to find a way to have only the first 180 degree turn and drop right into a muffler and then exhaust out the back of the muffler.

The problems I've run into is according to the Donaldson web site this is essentially the highest flow muffler they offer in the small space it occupies. I'd love to run the M090535, but don't know how I would get a 51" long muffler into the back of the bus.

So, I'm looking for ideas .... I want to stay with the 5" exhaust at a minimum.

Any thoughts on how to improve this setup?

Keep in mind the MCI muffler fits up between the tag tire and the bumper. The M120131 muffler is 29" long and there is no way I can see to put a longer muffler in the existing space unless I'm missing some reconfiguration options.

The book shows the ISM exhaust flow of a 500hp 2100 rpm engine at 2341. I don't know what hp you are running but your do need to delete some of those bends. Have you looked at the walker site to see if they might make something that would work for you. a side or top inlet with a end out let sounds like the one you would want.

Don,I'm running at 400HP, but can be reprogrammed to 450. So, I need to make sure I accomodate a 450HP setting if I ever decide to go that route. Can you look up the flow required at 450HP and 400HP? Also, what was the Hg back pressure allowed?

Walker mufflers? The website looks like an automotive website. Is there a particular page that would be a good starting point for me?

Stay with that same muffler but reposition it next to the transmission. Then you can run a pipe that is relatively straight back from turbocharger to the muffler by the transmission, then the tail pipe can come to the back of the bus by means of a relatively straight pipe also. Even running the pipe back almost to the rear axle, even though a longer distance, will again eliminate those 180 turns and be able to use much straighter lines.I have the same type of muffler, 5" same side inlet and outlet. When I bought it you could look inside and see no baffles. Even though I have 3 sharp 90 degree turns, it is still more free flowing than the giant stuffed up muffler (66" long and 13" in diameter) that was on it originally. Good Luck, TomC

Since you are looking at the exhaust side of things are you still running the stock intake sizes. Mostly wondering about the intake part that directly accesses the outside air. On my 8 it seems to be a rectangle affair just infront of the drivers side radiator. Looks a little small to me?

Yeah, my best guess here is that you have way too many bends in the pipe. Going to a larger flow muffler without addressing the root problem is not really going to help. Neither is going to a larger diameter pipe keeping all the bends of the same radius.

Someway we need to put on our thinking caps and come up with a good idea/plan to open up the restrictions with your exhaust system. Quiet is good here, along with MINIMUM turns and stuff. Perhaps you can send us some pics of your present system. Sure we can fit it.

Aero makes a high flow w/ 5" in/out. Supposed to increase HP & MPG.http://www.aeroexhaust.com/five_inch_muffler_5050xl.htmlI have a 90 / 90 on my 6V92 it seems to work fine. My turbo outlet faces the front of the bus also. I have a short straight then 90 w/ a short straight, then another 90 into the muffler, and a long bend 90 out beyond the body. If you can use long bend 90 that's better.